NEET-XII-Physics
09: Ray Optics And Optical Instruments
- #33An angular magnification (magnifying power) of 30X is desired using an objective of focal length 1.25 cm and an eyepiece of focal length 5 cm. How will you set up the compound microscope?
Ans : Focal length of the objective lens,.gif)
= 1.25 cm
Focal length of the eyepiece, fe = 5 cm
Least distance of distinct vision, d = 25 cm
Angular magnification of the compound microscope = 30X
Total magnifying power of the compound microscope, m = 30
The angular magnification of the eyepiece is given by the relation:
The angular magnification of the objective lens (mo) is related to me as:
= m
Applying the lens formula for the objective lens:
The object should be placed 1.5 cm away from the objective lens to obtain the desired magnification.
Applying the lens formula for the eyepiece:
Where,
= Image distance for the eyepiece = -d = -25 cm
.gif)
= Object distance for the eyepiece
Separation between the objective lens and the eyepiece
Therefore, the separation between the objective lens and the eyepiece should be 11.67 cm.